Abstract-In this paper, an advanced site-specific image-based ray-tracing model is developed that enables multielement outdoor propagation analysis to be performed in dense urban environments. Sophisticated optimization techniques, such as preprocessing the environment database using object partitioning, visibility determination, diffraction image tree precalculation, and parallel processing are used to improve run-time efficiency. Wideband and multiple-input-multiple-output (MIMO) site-specific predictions (including derived parameters such as theoretic capacity and eigenstructure) are compared with outdoor site-specific measurements at 1.92 GHz. Results show strong levels of agreement, with a mean path-loss error of 2 dB and a mean normalized-capacity error of 1.5 b/s/Hz. Physical-layer packet-error rate (PER) results are generated and compared for a range of MIMO-orthogonal frequency-division-multiplexing (OFDM) schemes using measured and predicted multielement channel data. A mean E b /N 0 error (compared to PER results from measured channel data) of 4 and 1 dB is observed for spatial-multiplexing and spacetime block-code schemes, respectively. Results indicate that the ray-tracing model successfully predicts key channel parameters (including MIMO channel structure) and thus enable the accurate prediction of PER and service coverage for emerging MIMO-OFDM networks such as 802.11n and 802.16e.

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Abstract-Rooftop diffraction can contribute significantly to the propagation path loss in outdoor microcellular environments. For non-coplanar multiple edges, the finding of exact ray paths requires a complex algebraic analysis that is infeasible for rapid application in deterministic ray tracing models. A new heuristic geometrical approach is reported that finds the ray paths for arbitrary height rooftop diffraction and rooftop-to-building corner diffraction. This method can be applied to any 3-D image based ray tracing model. The accuracy of the new method is first quantified using two specific test cases. The method is then implemented in an existing microcellular ray model and path loss predictions are compared with measured data. The heuristic diffraction approach is shown to be simple to implement and lowers the prediction error when compared with the traditional Vertical Plane diffraction approximation.

Abstract-In this paper an advanced site specific image-based ray-tracing model is developed that enables multi-element outdoor propagation analysis to be performed in a microcellular environment. Sophisticated optimization techniques such as preprocessing the environment database using object partitioning, visibility determination, diffraction image tree pre-calculation techniques, and parallel processing are used to improve run time efficiency. A comparison of path loss prediction with multielement site specific measurements shows strong agreement, with a mean error of 3.6dB and a standard deviation of 3.2dB. The model is also shown to be capable of performing detailed MIMO analysis.

Abstract-This paper presents a new hybrid geometrical optics (GO) and radiance based rough surface scattering model for use in ray tracing propagation models. The reflectance model includes the effects of both specular and diffuse reflection. The specular component is modelled using GO Fresnel reflections, while the diffuse components are modelled using radiance reflectance. The hybrid scattering model is then developed and implemented within an existing three-dimensional microcellular ray tracing model. Comparisons of predicted path loss and rms delay spread are made at 1.92 GHz using site specific measurements in an urban environment. The results demonstrate that scattering can be an important mechanism at this frequency. Significant improvements in prediction accuracy are demonstrated with the new hybrid scattering model.